/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#ifndef NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_POOL_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_POOL_H_

#include <vector>

#include "pagespeed/kernel/base/basictypes.h"

namespace net_instaweb {

class RewriteDriver;
class RewriteOptions;

// A class for managing recycling of RewriteDrivers with standard options.
// Note that this class by itself is not threadsafe, as ServerContext
// takes care of that.
class RewriteDriverPool {
 public:
  RewriteDriverPool();

  // Deletes all drivers in the pool.
  virtual ~RewriteDriverPool();

  virtual const RewriteOptions* TargetOptions() const = 0;

  // Return a driver from freelist, or NULL.
  RewriteDriver* PopDriver();

  // Stores the driver on freelist, and Clear()s it for reuse.
  void RecycleDriver(RewriteDriver* driver);

 private:
  std::vector<RewriteDriver*> drivers_;

  // Don't allow more than this many drivers in the pool. The pool is an
  // optimisation to save the cost of constructing a RewriteDriver, but keeping
  // a lot of them lying around winds up wasting a lot of memory instead.
  static const int kMaxDriversInPool = 50;

  DISALLOW_COPY_AND_ASSIGN(RewriteDriverPool);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_POOL_H_
